Abstract: The present invention relates to a process for chemical extraction of gold and silver from low grade and refractory pyritic concentrates containing minimum 1 ppm Au, by their leaching in enameled cast iron reactors, steel plated lead or plastic coated steel, at room temperature, in ammoniac solutions (pH 8-10) of sodium thiosulfate (50-60 g/l Na2S2O3. 5 H2O) with a divalent copper salt as catalyst (3-4 g/l Cu). The suspension resulting after 2-4 hours of reaction is filtered. The thiosulfate solution containing minimum 5 mg/l undergoes an electrolysis process with insoluble anodes. Copper, gold and silver is deposited in the cell as a sludge, and the electrolyte having a maximum content of Au of 1 mg/l, is recycled to the leaching operation of raw material, after correction of copper content and alkalinity to the baseline values.

Abstract: The present invention relates to a process for chemical extraction of gold and silver from low grade and refractory pyritic concentrates containing minimum 1 ppm Au, by their leaching in enamelled cast iron reactors, steel plated lead or plastic coated steel, at room temperature, in ammoniac solutions (pH 8-10) of sodium thiosulfate (50-60 g/l Na2S2O3. 5 H2O) with a divalent copper salt as catalyst (3-4 g/l Cu).The suspension resulting after 2-4 hours of reaction is filtered. The thiosulfate solution containing minimum 5 mg/l undergoes an electrolysis process with insoluble anodes. Copper, gold and silver is deposited in the cell as a sludge, and the electrolyte having a maximum content of Au of 1 mg/l, is recycled to the leaching operation of raw material, after correction of copper content and alkalinity to the baseline values.

Abstract: The present invention relates to an improved method for enzymatically removing blood type-specific antigens from erythrocytes, comprising titrating the pH of the erythrocytes first to a pH suitable for enzyme activity and then, once the desired extent of antigen removal has been achieved, to a pH appropriate for storage and/or transfusion. The buffers used for titration have pH values significantly above or below the target pHs for erythrocyte conversion or storage/transfusion. The invention is based, at least in part, on the discovery that the structural integrity of the erythrocytes is not substantially disrupted by titration. The present invention further relates to methods wherein the addition of polyethylene glycol improves the efficiency of enzymatic removal of erythrocyte antigens.

Abstract: This invention relates to a recombinant enzyme for use in the removal of A antigens from the surface of cells in blood products. Specifically, this invention is directed to a recombinant &agr;-N-acetylgalactosaminidase enzyme from chicken liver, methods of cloning and expressing said recombinant &agr;-N-acetylgalactosaminidase enzyme and a method of removing A antigens from the surface of cells in blood products using said recombinant &agr;-N-acetylgalactosaminidase enzyme.

Abstract: The present invention relates to purified and isolated nucleic acid encoding the endo-.beta.-galactosidase from Flavobacterium keratolyticus (referred to as "ENDO-A"), and to purified ENDO-A protein. The endo-.beta.-galactosidase of the invention may be used in a process which enzymatically de-antigenizes human erythrocytes bearing A.sub.1 antigen. The resulting erythrocytes may be transfused into individuals who would be otherwise unable to tolerate a transfusion of type A.sub.1 blood.

Abstract: This invention relates to an improved method of purifying the enzyme .alpha.-N-acetylgalactosaminidase from avian liver, as well as to the purified enzyme. The enzyme is capable of removing A antigens from the surface of cells in blood products. The method of purifying the enzyme is simple and time efficient, and lends itself to large scale production.

Abstract: Type O erythrocytes are produced from certain subtypes of A erythrocytes or type AB erythrocytes by contacting the same following equilibration of a pH of 5.6-5.8 with an .alpha.-N-acetylgalactosaminidase, preferably obtained from an avian liver, for periods sufficient to convert the A antigen in the erythrocyte to the H antigen. Following removal of the enzyme, the erythrocyte is re-equilibrated to a pH of 7.2-7.4. As a result, there is obtained O type erythrocytes characterized by a 60 to 90 percent ATP level based on the level of ATP in naturally occurring O or AB erythrocytes. Beginning with certain A cells one obtains synthetic O erythrocytes characterized by a terminal .alpha.-fucose moiety, O antigenicity, and the absence of A antigenicity. Beginning with A.sub.2 B erythrocytes, one obtains B erythrocytes by the same process characterized by the absence of A antigenicity, greater H antigenicity than naturally occurring A.sub.2 B cells, the presence of B antigenicity and the aforedescribed ATP levels.

Abstract: Transfusable type O erythrocytes free of P1 antigenicity which are produced by an alpha-galactosidase conversion of type B antigen to type H antigen. The resulting erythrocytes retain a high level of ATP and 2,3 DPG.

Abstract: A composition comprising type O erythrocyte free of P.sub.1 antigenicity; a method of converting erythrocytes of the B antigen type to erythrocytes of the H-antigen type which comprises:A. equilibrating said erythrocytes to a pH of 5.7-5.8;B. thereafter contacting the so-equilibrated erythrocytes with an enzyme for a period sufficient to convert the B antigen in said erythrocytes to the H-antigen;C. thereafter removing said enzyme from said erythrocytes andD. re-equilibrating said erythrocytes to a pH of 7.2-7.4.The specification discloses conversion of the B antigens in human and animal blood to the H antigen (O cells).